Sleep Deprivation Affects Multiple Distinct Cognitive Processes

Article excerpt

Sleep deprivation adversely affects the ability to perform cognitive tasks, but theories range from predicting an overall decline in cognitive functioning (because of reduced stability in attentional networks) to claiming specific deficits in executive functions. In the present study, we measured the effects of sleep deprivation on a two-choice numerosity discrimination task. A diffusion model was used to decompose accuracy and response time distributions in order to produce estimates of distinct components of cognitive processing. The model assumes that, over time, noisy evidence from the task stimulus is accumulated to one of two decision criteria and that parameters governing this process can be extracted and interpreted in terms of distinct cognitive processes. The results showed that sleep deprivation affects multiple components of cognitive processing, ranging from stimulus processing to peripheral nondecision processes. Thus, sleep deprivation appears to have wide-ranging effects: Reduced attentional arousal and impaired central processing combine to produce an overall decline in cognitive functioning.

Sleep deprivation is a manipulation that allows arousal levels to be manipulated to a higher degree than one sees in the experimental interventions typically used in cognitive research. The effects of acute sleep deprivation on cognition are reversible, so sleep deprivation represents a different approach for investigating the underlying processes of cognition. Conversely, carefully selected tests of cognitive processing can provide new information about the effects of sleep deprivation on the brain.

Experimental and modeling studies of the effects of sleep deprivation on cognitive performance have thus far focused almost exclusively on global outcome measures (Durmer & Dinges, 2005; Van Dongen, 2004). Such research has revealed that overall performance declines as a function of time spent awake, modulated by circadian rhythm (Van Dongen & Dinges, 2005). However, not much is known about the effects of sleep deprivation on detailed performance outcomes, such as response time (RT) distributions, or on changes in specific cognitive components, such as decision processes. Attempts are being made to bridge this gap with the use of computational modeling that is based on cognitive architectures (Gunzelmann, Gluck, Price, Van Dongen, & Dinges, 2007), but these efforts need to be informed by precise information regarding which component processes of cognition are affected by sleep deprivation and how.

The present study addressed this issue. Participants were tested on a two-choice numerosity discrimination task at baseline after 57 h of sleep deprivation and again following 2 days with recovery sleep. Participants in a control group were tested at the same times, but without sleep deprivation. In each trial of the two-choice task, between 31 and 70 asterisks were placed in random positions in a 10 × 10 array, and the participants were instructed to judge whether the number was greater than 50 (large) or less than 50 (small). This task was selected because it has few memory demands or perceptual limitations (such as brief presentation or low contrast), allowing us to focus on central cognitive processes and decision processes.

We applied the diffusion model (Ratcliff, 1978, 1988; Ratcliff, Cherian, & Segraves, 2003; Ratcliff & McKoon, 2008; Ratcliff & Smith, 2004; Ratcliff, Van Zandt, & McKoon, 1999; Smith, 2000; Smith, Ratcliff, & Wolfgang, 2004; Voss, Rothermund, & Voss, 2004) to the data from each individual participant. From this, we were able to obtain estimates of the model parameter values for the baseline, deprivation, and recovery sessions in the experimental group, as well as for those in the control group. These parameter estimates allowed us to draw conclusions about the effects of sleep deprivation on components of cognitive processing.

Method

Participants

A total of 25 participants (13 women; age range, 22-38 years) completed the study. …